Camera: Set the width dynamic to parent from fixed 400px

Width of the seekbar was 400px and that caused overflow for
the rightmost text value.

Set the width match_parent so that it'll change dynmaically
with the text window.

Change-Id: I51069d4c5687e72516bc4a5afc59f9f3ae6f8e88
CRs-fixed: 582325